1. Field of the Invention
The present invention relates generally to drive system configuration and operation in electrophotographic (EP) printing machines, and, more particularly, to a drive system with multiple motor-and-gear-train configurations for reduction of jitter and noise and shutoff of color developer drive assemblies during black only mode operation for preservation of color developer useful life in the EP printing machine.
2. Description of the Related Art
Through a variety of mechanisms, engaged or meshed mechanical gears, or gears and pinions, generate vibration, or jitter, and noise while running. While gears meshing under load will generate some noise, the level of noise is exacerbated when the gears are subjected to unsteady and/or unbalanced forces. Tooth-to-tooth spacing errors, gear teeth elasticity, and intentional and unintentional deviations of tooth running surfaces from ideal configurations, generate unsteady forces and motion that results in vibration and noise. Such noise and vibration sources may be found in a wide variety of gear types, including spur, helical, worm and bevel type gears. By way of definition, gear mesh frequencies come from the individual impacts of gear teeth against each other, and the gear mesh frequency is equal to the number of teeth on the gear times the gear (or rotor) speeds, in revolutions per minute (rpm). In other words, mesh frequency is the rate at which gear teeth pairs contact as they pass through mesh, expressed in Hz.
The vibration (and noise) spectra generated by meshed and running gears is primarily tonal in nature. There are strong tones corresponding to the gear mesh frequency and harmonics thereof. In addition, there are tones corresponding to the rotation rate of each gear, and harmonics thereof. Gear mesh tonal noise is different from and in addition to tonal noise that appears at frequencies related to the passage of armature slots within the motors, or related to harmonics of line frequency if an SCR drive is used. Furthermore, gear mesh noise is present regardless of the type of prime mover or drive mechanism.
Vibration, or jitter, and noise normally accompany satisfactory operation of many machines utilizing motors and gear trains for transmitting motion. Electrophotographic (EP) printing machines are no exception. It is a characteristic of EP printing machines that they typically involve repetitive starts and stops in the normal course of their operations such that engaging and meshing of gears over the operating life of the EP machine gradually and inevitably contribute to a normal expected level of gear wear, vibration or jitter and noise.
Unfortunately a further characteristic of EP printing machines also contributes to gear wear, vibration or jitter and noise over and above this expected level. This characteristic is that it is the inherent nature of EP printing machines that many of their major functional components are consumables and thus must be replaced by new ones after differing periods of usage over the operating lifetimes of the machines. These consumable components include toner cartridges, developer units, photoconductive (PC) drum units, fuser units and the like. (The PC drum unit and toner cartridge are typically a two-piece consumable component where the toner cartridge fits into the PC drum unit; then they slide together into the machine. These two consumables typically have different periods of usage with the PC drum being the longer of the two.) Each consumable component has gear(s) which mesh with corresponding gears of the drive train in the machine. The drive train components, however, are usually not part of the consumable items and so remain with the machine while the consumable components are replaced, some many times during the operating life of the machine. These non-replaced drive train components will inherently undergo wear over time and so each time a new consumable component is installed in the machine an old, worn gear of the drive train must interact and mesh with a new, non-worn gear of the replacement components. Sub-optimal gear engagements will frequently result due to even small losses of control over gear center distances and imposition of unbalancing forces as a result of these interactions and also from the repeated separating and re-engaging of gears in the recurring making and breaking of the drive train couplings with the consumable components. Thus, further increased vibration, or jitter, and noise may occur above the normal expected levels.
One approach to addressing the problem of gear mesh vibration and noise is disclosed in U.S. Pat. No. 5,809,843 to Barger et al. This patent proposes to cancel gear vibration and noise at gear meshing frequencies by imposing a canceling drive torque or force on a driven gear set. To accomplish this, sensors are located proximate to meshing gears to receive information representative of vibration and noise generated at the meshing gears. The noise information received is provided to a control mechanism that processes the noise information to generate a corresponding drive torque. The drive torque so generated corresponding to the noise information is applied to a drive shaft to reduce vibration and noise of the gear assembly at gear meshing frequencies. The drive torque applied to the drive shaft is thought to constitute an appropriate corrective torque and/or linear force to impose on a gear/shaft combination to effect a displacement at the gear tooth meshing interface so as to cancel the effects of imperfections including those attributable to gear tooth spacing, tooth shape, or the like. The corrective torque or force is imposed with an appropriate frequency content, amplitude and phase that result in desired noise and/or vibration reduction at points of interest. Thus, the approach of Barger et al. is primarily one of gear mesh vibration and noise generated feedback and cancellation at gear meshing frequencies.
While the approach of Barger et al. may be satisfactory in use for the specific applications for which it was designed, for example, electric motors, gas turbine systems, diesel generators, internal combustion engines or the like, it does not seem to be an appropriate approach calculated to provide a practical solution to the problem of vibration, or jitter, and noise as generated in EP printing machines. It would likely cost too much to try to implement and be highly unlikely to function satisfactorily in the start and stop operational environment of an EP printing machine. It appears to constitute a solution that is intended to operate at a level of precision that is not likely to be achievable or necessary in the EP printing machine operating environment.
Thus, there is still a need for an innovation that will overcome the above mentioned problem of machine gear mesh vibration, or jitter, and noise in a cost-effective manner.